a. Field of the Invention
The present invention relates to support mechanisms in seats and, in particular, to a convenient trunk support mechanism for a wheelchair.
b. Prior Art
By way of introduction, FIG. 1 illustrates a wheelchair seat 10 according to the present invention, on which is mounted a trunk support mechanism 12. The trunk support mechanism 12 serves to limit the lateral range of motion of the patient, so that his or her torso does not shift to the left or right within the wheelchair. The seat 10 of FIG. 1 is a prototype that is presented here strictly for the purpose of illustration, and it has a trunk support mechanism on only one side of the seat. In practice, the respective trunk support mechanisms will be mounted on both the left and right sides of the seat.
Continuing our introduction, the seat 10 of FIG. 1 has a bottom cushion 14 and a back seat cushion 16. A pelvic stabilizer mechanism 18 serves to retain the patient""s pelvis within the chair. A suitable pelvic stabilizer is described in a co-pending patent application filed concurrently herewith entitled xe2x80x9cPelvic Stabilizer Mechanism for a Wheelchairxe2x80x9d and in U.S. Provisional Patent Application No. 60/130,046, both of which are incorporated by reference herein. In practice, the seat 10 will be mounted on a base having wheels and other components that are typical of a wheelchair.
FIG. 2 illustrates a prior art trunk support mechanism 20 that is awkward to use. The mechanism includes a padded trunk support arm 22. The mechanism is mounted on the rear of the back seat cushion 24 with a mounting mechanism 26. The trunk support mechanism 20 has a hinge 28, with a rear hinge portion 30 and a front hinge portion 32. The trunk support mechanism is in a locked position in FIG. 2, but it can be disengaged from the locked position so that the support arm 22 can swing outwardly and away from the patient. The arm is normally swung outwardly when the patient is being put into or removed from the seat, or when the patient""s position must be changed.
The prior art mechanism of FIG. 2 is cumbersome to use. The user must lift up on the front hinge portion 32 at a specific point 34 (FIG. 3) in order to disengage a spring-loaded pin (not shown) in the upper portion 36 of rear hinge portion 30 from engagement with a receptacle 38 (FIG. 4) that has an indentation to receive the spring loaded pin. The mechanism is awkward to use because the user must push up at exactly point 34, or the rear and front portions of the hinge will not disengage from one another, and the hinge will not rotate. Even when the user does push up at the proper point 34, the patient must be moved off to one side of the seat, so that he or she is not leaning against the trunk support mechanism 20. Otherwise, the weight of the patient prevents the user from unlocking the support arm and, again, the arm will not unlock.
U.S. Pat. No. 5,678,798 to Little discloses a swing-away support bracket having a housing, an axle mounted for rotation in the housing, a toggle with a protrusion, and a tapered recess in the axle to receive the protrusion. To lock the swing-away support bracket, the user engages the protrusion into the axle. The arrangement is inconvenient, because the toggle is located within a narrow recess in the housing. The lock is also weak, because the protrusion on the toggle is small, with only a small portion of the toggle engaging with the tapered recess.
Broadly defined, the present invention is a support arm mechanism that is simpler and/or more reliable in use than support arm mechanisms of the prior art. The invention also relates to an improved hinge that can be used in a trunk support arm mechanism, and in other applications.
One embodiment of the present invention is a locking trunk support hinge that is convenient to lock and unlock. For example, the hinge can have a lock with a front hinge portion and a rear hinge portion. A locking member, having a locking head and a lever, is rotatably mounted to one of hinge portions, and a locking channel extends in the other one. The hinge has a locked mode in which the locking head is engaged in the locking channel and the hinge cannot be swung, and an unlocked mode in which the locking head is not engaged in the locking channel and the hinge can be swung open. The locking mechanism can have a compression spring that biases the locking head into the locked mode when the front and rear hinge portions are aligned.
In accordance with a particular embodiment of the present invention, a durable locking mechanism for a wheel chair trunk support apparatus has a back bracket, a front bracket, and a hinge piece that extends from the back bracket toward the front bracket. The hinge piece has a top and a bottom, with the bottom including an elongated open channel defined by first and second walls. A locking member is rotatably mounted on the front bracket. The locking member has an angled lever and an elongated locking head that is configured to fit within the open channel of the hinge piece. The lever extends downwardly from the front bracket, and the locking head extends forwardly. The locking mechanism has a first, locked mode in which the locking head is situated within the open channel and in between the first and second walls, and a second, unlocked mode in which the locking head is situated outside of the open channel. The locking mechanism may also include a compression spring mounted within the hinge piece and adjacent to the locking member, to maintain the locking head in the open channel when the locking mechanism is in the first, locked mode.
Particular embodiments may incorporate various features. For example, the locking head may be at least xc2xd inch long. The front and rear brackets and the hinge piece may be xc2xdxe2x80x3 or less thick in order to limit the bulk of the support. In the locked position, the entire length of locking head may be engaged in the locking channel. The lever of the locking member may extend at an angle of between about 10 degrees and 60 degrees, and preferably from between about 20 degrees and 45 degrees, downwardly from the front bracket. This angled lever provides a convenient means of engaging the locking member to unlock the hinge mechanism. The lever and hinge member are typically metal, and portions of the mechanism may be made from steel for particular strength and durability. The hinge piece may be separate from but attached to the front bracket, or it may be unitary with the front bracket. The trunk support may be one component in a convenient system for releasably retaining a person in the wheelchair. Such a system can include a wheelchair seat, a trunk support mechanism as described above, and a pelvic support mechanism as described in a co-pending patent application filed concurrently herewith entitled xe2x80x9cPelvic Stabilizer Mechanism for a Wheelchairxe2x80x9d and in U.S. Provisional Patent Application No. 60/130,046.
Various other objects and features of the invention will become apparent in the Detailed Description below, in the drawings and in the claims.